The treatment of acute and chronic spinal instabilities or deformities of the thoracic, lumbar, and sacral spine has traditionally involved the implantation of rigid rods to secure the vertebrae of a patient. More recently, flexible materials have been utilized in connection with securing elements, such as pedicle screws, to provide a dynamic stabilization of the spine. Such dynamic stabilization systems typically include a flexible spacer positioned between pedicle screws installed in adjacent vertebrae of person's spine. Once the spacer is positioned between the pedicle screws, a flexible cord is threaded through eyelets formed in the pedicle screws and an aperture through the spacer. The flexible cord retains the spacer between the pedicle screws while cooperating with the spacer to permit mobility of the spine. One drawback of traditional implantation of such dynamic stabilization systems is that relatively large surgical sites are required to permit threading the cord through the screws and spacer once the spacer has been positioned between the screws.
While some dynamic stabilization systems have been proposed for permitting the top loading of a spacer and cord between pedicle screws using guide rods to direct the cord and spacer between the screws, these systems also require a relatively large surgical sites and present difficulties when the curvature of the spine causes a convergence of the guide rods that makes it difficult to position the spacer between the guide rods.
A need therefore exists for a spinal dynamic stabilization system that overcomes these and other drawbacks of the prior art.